(1) Field of the Invention
The present invention relates to a slidable assembly which travels along the image of an original document in order to read the original image, in an image reading unit, scanner unit etc., provided in an image forming apparatus such as a copier, printer, facsimile machine.
(2) Description of the Prior Art
A typical digital copier has a pair of slidable assemblies which are made to travel along the original table, in order that an image reading unit can optically read the image of an original placed on the original table. One, the first, slidable assembly is composed of a light source for illuminating the original placed on the original table and a reflection mirror for reflecting the reflected light from the original illuminated by the light source. The other, the second, slidable assembly has a pair of reflection mirrors which deflect the light from the reflected mirror from the first slidable assembly to the opposite direction. Both the slidable assemblies are moved in the same direction along the original table. The light emitted from the light source provided in the first slidable assembly to the original placed on the original table is reflected by the original. The reflected light is further reflected by a pair of reflection mirrors on the second slidable assembly which is disposed at a site opposite to the scan direction and deflected by 180xc2x0 so that the reflected light will be incident on the photoelectric converting layer of a photoelectric conversion device fixed at the predetermined position.
The traveling speed of each slidable assembly is set so that the optical length of the light reflected from the original to reach the photoelectric conversion device is constant.
Each slidable assembly extends in the direction perpendicular to the scan direction in order to illuminate the whole face of the original placed on the original table, each end being guided along the flat surface of a corresponding guide element arranged in the scan direction.
Slider pieces which slide in contact with the flat surface of the guide elements are attached at the ends of the slidable assembly. Each slider piece is made up of a resin or the like that has a low coefficient of friction against the guide element and is secured to the slidable assembly by, usually, screws etc.,
However, since screws etc. are needed to attach the slider pieces at predetermined positions in the slidable assembly body of the slidable assembly of the above configuration, assembling takes up time, thus producing a loss of economy. Further, a long use of the slider pieces that frictionally move over the guide elements may cause such risks that the frictional force against the guide element may wear the slider pieces or a strong stress may act on the portions fixed by screws etc., damaging the slider pieces. Once a slider piece breaks, the replacement work needs time and labor for repairs, resulting in degraded service performance.
The present invention has been devised to solve the above problems and it is therefore an object of the present invention to provide a slidable assembly wherein slider pieces sliding on the guide elements can readily be attached to the slidable assembly body and yet the slider pieces can be positioned appropriately and the slider pieces are free from unwanted vibrations, which can prevent generation of chattering sounds from unstable sliding.
In order to achieve the above object, the present invention is configured as follows:
In accordance with the first aspect of the present invention, a slidable assembly comprises: a slidable assembly body; and slider pieces sliding over guide elements and attached to the slidable assembly body, the upper part of the slider piece being an insert portion which is fitted through a passage hole formed in the slidable assembly body and has engaging portions that deform so as to pass through the passage hole and become engaged with the rim of the passage hole, wherein each engaging portion is deformed in a direction different from the sliding direction.
In accordance with the second aspect of the present invention, the slidable assembly having the above first feature is characterized in that the passage hole has a shape that is elongated in the sliding direction of the slider piece and the insert portion of the slider piece has a cross-section similar to that of the insert hole.
In accordance with the third aspect of the present invention, the slidable assembly having the above first feature is characterized in that the slider piece has a flange which holds the rim of the passage hole in cooperation with the engaging portions when the insert portion has been fitted through the passage hole.